The regulation of food intake in normal and obese monkeys is the primary focus of the proposed research project. Initial studies will describe the normal feeding behavior and metabolic profile of primates to elucidate the effects of different feeding schedules and dietary compositions on body weight, adiposity, total intake, and metabolic pathways. Both spontaneously obese and VM lesioned obese monkeys will be studied under the same conditions and will be compared to each other and to normal monkeys for cues to critical differences in regulatory mechanisms and behavior. Recognizing that complex interactions of both hormones and fuel substances probably underlie the regulation of intake and body composition, it will be important to examine a number of the potential signals simultaneously and under varied conditions. Hypotheses concerning potential blood-borne factors in feeding regulation will be further tested by two methods designed to examine the effects of alterations in these humoral constituents. Cross circulation will be carried out between pairs of monkeys differing in deprivation state and/or body fat stores with simultaneous assessment of blood-borne constituents and feeding behavior. Intravenous and intraarterial infusions will be used to test hypotheses formulated on the basis of the normative, obesity and cross circulation experiments. Results will contribute to the early detection and possible prevention or therapeutic management of obesity and other disturbances of feeding and regulation.